ES2972530T3 - Drone detection radar - Google Patents

Abstract

A drone detection radar comprises a plurality of antenna systems, each antenna system being arranged to transmit a signal to an associated sector and to receive reflected signals from targets in the sector, the sectors collectively forming a monitored volume, and in the that a subset of the antenna systems are active at any time, the active subset of antenna systems being arranged to monitor their respective volumes for a time sufficient to measure Doppler signals associated with slow-moving drones, the radar being arranged to switch to a different subset of antenna systems after each duration, so that the entire volume is monitored within a predetermined period. The combination of an observation array of an antenna system with a plurality of switched antenna systems makes it possible to detect and track drones, with the appropriate selection of the predetermined period. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Drone detection radar

The present invention relates to a system and method for detecting targets using a radar system. More particularly, it relates to a system and method for operating said radar in a manner that improves the probability of detection of drones as a target object.

In recent years, the availability of helicopter models, remotely piloted aerial systems (RPAS), unmanned aerial vehicles (UAVs), multirotors and similar remotely controlled aircraft of various types and sizes has increased dramatically, in part due to the cost decreasing technology that allows them to fly without much skill and training. Such aircraft (generally referred to here as drones) are often purchased as toys, but are often capable of carrying payloads such as cameras or other relatively light objects. This ability makes them useful for transporting objects to hard-to-reach places or carrying out monitoring or surveillance work.

It didn't take long for them to be used for socially undesirable or illegal tasks. A growing problem is the use of drones to carry contraband into prisons, by flying the drone over a wall and landing it in an exercise yard or similar area. Other undesirable uses of drones include incursions into protected airspace or invasion of privacy in sensitive areas.

Therefore, the need has arisen to be able to detect the use of drones.

Acoustic sensors can be useful at very close range, but their usefulness deteriorates in noisy urban environments. Video systems, including infrared imaging systems, are useful for confirming a detected drone presence, but also suffer when in visually cluttered environments or in poor weather conditions and in the dark, again often having difficulty in detect drones at longer distances (such as more than several tens of meters), a wide-angle lens provides good angular coverage but cannot detect the drone at longer distances, while telephoto lenses provide good performance at long distances, but only with a very narrow field of vision.

Radar systems can be used, but because the speed of drones is so variable and often zero, they can easily be caught by the clutter filtering that radars typically use to eliminate returns from static objects. Their speeds and flight characteristics also tend to match those of birds, so radars have been prone to high false alarm rates when used against drones.

US Patent Publication No. 2015/323658 A1 describes a solid-state marine radar technology based on a non-rotating cylindrical array antenna. Multiple transmit/receive modules are used to form the antenna beam, allowing beam sequencing, dwell time at each beam position, resolution, and beam shape to be varied to make the best use of available power. . High duty ratio waveforms can be used in transmission to make efficient use of solid-state power amplifiers.

The present invention aims to provide a means for drone detection that at least improves one or more of the disadvantages of the prior art.

According to the invention, there is provided a drone detection radar comprising five panels, each of which includes an antenna system, the panels being arranged on or within an enclosure that holds the panels in predetermined positions, the enclosure It comprises a quarter sphere around which the panels are arranged. and wherein three of the panels are located in a lower row of the enclosure and two of the panels are located in an upper row of the enclosure. Each antenna system is arranged to transmit, using a transmitter, a signal to an associated sector, and to receive, using a receiver, reflected signals from targets in the sector, where the sectors associated with the antenna systems collectively form a volume monitored, and wherein a subset of the antenna systems is active at any given time, wherein each subset of the antenna systems is arranged to monitor its respective sector(s) for a time before a failure occurs. switch to another subset, with the radar arranged to switch to a different subset of antenna systems after each duration, so that the entire volume is monitored within a predetermined period. The duration for each respective sector is up to 0.2 seconds, and each antenna system is arranged to monitor a sector of approximately 60° in azimuth and 45° in elevation.

Therefore, the invention provides benefits associated with fixed radars, that is, radars that have a long static view of a scene and are therefore capable of measuring signals that have low Doppler frequencies, while providing the benefits of radars that have antennas that can change the direction of sensitivity, thus allowing a wider volume to be scanned, compared to a normal fixed radar.

Advantageously, in some embodiments, the entire volume may be monitored every two seconds, or every second, half second or quarter second. The nature of drones, and their typical flight patterns and speeds, is such that several (e.g. 3, 5, 10 or 15) separate panels, and therefore sectors, within the volume of interest, while maintaining a sufficient time spent on each one, and also maintaining sufficient follow-up on an objective. Preferably, a dwell time is provided in each sector of between 50 ms and 0.5 s, and more preferably the dwell time is between 70 ms and 0.2 s. Some embodiments may have a dwell time of approximately 0.1 s. The Doppler signals associated with the drone may be those from the body, one or more of the drone's motors, or one or more of the drone's blades, and may comprise one, two, or all three.

Some implementations may have a variable residence time in each sector. For example, the radar system may be arranged to change dwell times in those sectors in which a target has been confirmed. The dwell time can be increased, for example, to allow improved measurement accuracy of a target. Alternatively, it may be reduced to allow greater dwell time, and therefore greater sensitivity, in other sectors where targets have not been detected, but where it is suspected (for example, based on other intelligence) that they are present. Tracking accuracy can be achieved by increasing the rate at which a given sector (for example, one in which a target has been detected) is visited, for example, by decreasing the time spent in some or all sectors, or by changing the switching sequence to prioritize those sectors where a target has been detected.

Conveniently, each subset of antenna systems may comprise a single radar antenna system (generally comprising a pair of transmit and receive antennas, although in some embodiments the same antenna could be used for both purposes). Therefore, such an embodiment may comprise a radar having n antenna systems, where each antenna system is activated in turn, for at least a minimum period of typically 0.05 s, and where a complete switching cycle is completed in no more than 2 seconds. Therefore, the minimum period and the duration of the full cycle can be adapted to the number of antenna systems that make up the radar and the size of the volume being monitored.

Each receiving antenna in an antenna system is preferably arranged to receive signals from targets within a sector covering one-fifteenth, one-tenth or more preferably one-fifth, one-quarter or one-third of a volume of interest. Therefore, the entire volume of interest can circulate relatively quickly, compared to many radars that have mechanically or electronically scanned antennas. This allows for relatively fast updating while providing sufficient dwell time within the monitoring sector of a particular antenna system to detect the target drone.

Advantageously, in each panel there is a transmitting antenna and a receiving antenna, which together form a single antenna system. This is particularly advantageous when the transmitted signals are CW (carrier wave), such as FMCW, or when the receiving antenna operates as a phased array (which may or may not be a phase-variable (steerable) phased array). Alternatively, a common antenna can be used for both transmission and reception. Advantageously, each panel has a plurality of elementary receiving antennas that collectively form the receiving antenna, which are arranged to produce a plurality of receiving beams. Conveniently, the receiver beams can be configured as fixed and static receiver beams, which can be combined in the processor (or in a separate beamformer) in a beamforming operation, to provide improved angular resolution of detected targets within the sector. . Elementary receiving antennas may advantageously be arranged to allow their elementary beam patterns to be vector-summed or otherwise combined, thereby allowing the use of super-resolution techniques, such as monopulse or the like, to provide greater angular precision. By such combinations multiple receiving beams can be produced. The combination may also advantageously include adjusting the phase or amplitude of the received signals, to change the effective direction of maximum sensitivity of the combined beam(s). Preferably, the plurality of elementary antennas are arranged in an n by m array, where n and m are at least 2, and may be equal. Therefore, super-resolution processing can be performed in both azimuth and elevation. Note that a panel may be a physical panel which may be, for example separable as a radar unit, or may comprise a radar area, the area forming a fictitious panel.

More advantageously, the radar may comprise five antenna systems, arranged to monitor a volume of 180° in azimuth and 90° in elevation. Alternatively, the radar may comprise ten antenna systems, arranged to monitor a volume of 360° in azimuth and 90° in elevation.

Each panel may further comprise a front-end RF circuit consistent with a radar system. Therefore, the transmit side may comprise an upconverter and a power amplifier, and the receive side may comprise a low noise amplifier and downconversion means. Some embodiments may employ an analog beamformer and/or a digitizer in the panel. Some embodiments may have digital beamforming performed on the panel, while others may have such functionality employed centrally, for all panels. Some embodiments may have the beamforming function distributed among a plurality of different beamforming operations, which may be all digital, all analog, or a combination of both.

To keep costs low, each panel may advantageously be substantially identical and may be arranged to connect to a central control unit comprising at least the processor and memory. The radar may also comprise central waveform generating means, such as a signal generator, which is then distributed to the panels.

The enclosure can house the processor, storage, and other items such as a power supply.

Advantageously, some embodiments of the invention may have a processor that is arranged to control the panels to activate them in sequence, scanning the volume under observation one or more sectors at a time. Some embodiments may choose to operate a single panel at a time, to keep data processing requirements at more modest levels to reduce cost. Others may choose to operate two or more panels simultaneously, for example having a higher refresh rate.

The processor may be arranged to provide an alert if signals are characteristic of being reflected from a drone, or may be arranged to display targets on a screen.

For those embodiments that employ a series of elementary receive antenna elements, which together form a receive antenna, other forms of multiple beam processing may be employed, such as electronic switching of the direction of the receive beam or otherwise , scan a receiving beam. Such a technique is useful for obtaining improved precision measurements of a target that has been confirmed to be of interest. Conveniently, each panel can be arranged to provide multiple beams simultaneously, which can be processed, for example, as described above, to provide additional gain and/or angular precision. Each panel can be arranged as a fixed array, which is activated and deactivated in sequence.

Advantageously, some embodiments of the invention may have an interface for connection with other radars, to allow the system to synchronize with similar connected radars to avoid unwanted interference between them. This can be achieved, for example, by ensuring that the radar does not transmit to a sector (and/or adjacent sector) that is being illuminated by another radar, or in which another radar is located, to avoid sending energy directly towards another radar while that other radar is receiving from the direction of the first, or towards a target illuminated by another radar, which may cause noise or interference. It can also be used to provide a bi-static or multi-static installation, in which one radar acts, at a given instant, as a transmitter, while one or more radars are arranged to receive the signal (or its reflections from the targets).

Therefore, some embodiments of the invention may comprise a plurality of radars, each of the type described above, wherein each of the plurality of radars is arranged within a neighborhood and is synchronized using an interface, such that they cannot transmit two radars in a sector visible to two or more radars within the neighborhood at a given time.

Furthermore, some embodiments of the invention may comprise a plurality of radars, each of the type described above, wherein each of the plurality of radars is arranged within a neighborhood and is synchronized using an interface, such that it is not allowed to two radars transmit to each other simultaneously within the same or nearby frequency band.

The interface connecting two or more radars together can also be used to provide a communications link between radar systems forming a network, where each radar in the network can be controlled to synchronize its switching with other radars in the network. Each radar can be additionally controlled to use different frequencies or transmission bands than others in the network, where interference might otherwise occur. One or more radars can be arranged in a group to adapt their operating frequencies, either by manual control by a human controller, or by automatic detection or prediction of interference based on reception of the interference or prior knowledge (for example, transmitted to through the network) of the operational characteristics of neighboring radars. The interface can also be used to share data on detected targets, to allow multiple radars to coordinate detected targets and trajectories between them.

In some embodiments, a separate controller may be used to control each radar and determine a transmission timing arrangement to avoid the aforementioned crashes. The independent controller can also control the channels or frequency bands of each radar system in the network. Alternatively, one of the radars in the network can function as a control radar that performs these functions.

Advantageously, some embodiments of the invention may have an interface (which may be the same or different from that mentioned above) to allow integration with a computer that provides a user interface. The computer may also allow integration with other sensors, such as audio or video sensors.

Advantageously, some embodiments of the invention may have an interface (which may be the same or a different interface than those mentioned above) that allows connection to a separate system that can be used to further identify the target, such as an electro-optical system, or to a system used to counter the target in some way. The electro-optical system may comprise, for example, a camera. The system to counter the target in some way may comprise any suitable countermeasure of a drone, such as an electromagnetic, laser or sonic jammer or directed energy weapon, or a system that directs a projectile or net at the target, or means to mount a cyberattack on the drone's internal communications or processing, or any other suitable system. It may also comprise means for notifying a human operator of the presence of the target, the current position of the target, the probable position of origin of the target (by examining its positional history) and/or the speed, height and/or or current direction of the target. It can also guide the operator to the current position or origin.

Advantageously, some embodiments of the invention may have an interface (which may be the same or a different interface than those mentioned above) that allows a connection between radars that facilitates cooperation regarding the monitoring of particular sectors of interest. For example, a first radar located near a large building may be arranged to have a shorter range, to exclude processing of returns from the building, while a second radar may be arranged to monitor beyond the building in sectors not covered by the first radar.

The invention will now be described in more detail and by way of example only, with reference to the following figures, of which:

Figure 1 shows a block diagram of one embodiment of a radar of the present invention;

Figure 2 shows an enclosure design for one embodiment of the present invention;

Figure 3 shows an arrangement of three radars of the present invention arranged to view a neighborhood; and

Figure 4 shows the approximate transmission and reception coverage for a five-panel radar.

Figure 1 shows a simplified block diagram of an embodiment of the present invention. This embodiment has five panels 10, of which one is shown in detail. Each panel is substantially identical in nature and has antennas and front electronics, forming an antenna system, mounted thereon. All panels have in common a processor 12, which also acts as an interface to a common waveform generator 14, as well as providing an interface to external systems, such as a display and controller, and to other radars.

Each panel 1 comprises a transmitting antenna 16 and a transmitting circuit 18, which includes a transmitting amplifier. A receiving antenna 20 is located adjacent to the transmitting antenna 16 and is connected to the front-end circuitry of the receiver 22 containing amplification and downconversion circuitry. A digitizer 24 is connected to an output of the receiver 22, which digitizes the output and provides its digitized outputs to the processor 12.

The processor also controls an enable function 26, which enables one (or, in some other embodiments, more than one) of the panels, while disabling the remaining ones.

It will be apparent to a person of ordinary skill that there are various interconnections between the components shown and functions (such as power supplies, switching and routing components, etc.) that have not been shown but that will be necessary to produce a functional system.

In operation, the processor 12 chooses a panel to activate, by appropriately controlling its enable line for each panel. With a panel enabled, the processor controls the waveform generator to generate waveforms appropriate for upconversion and transmission by the transmitter 18 and antenna 16 on that panel. The receiver antenna 20 and the front end of the receiver 22 receive signals such as any reflections of signals transmitted from objects in a volume to be monitored. The receiving antenna 20 consists of nine sub-antennas, in a 3 x 3 square array, each of which has its own receiving circuit. The receiving circuit 22 amplifies, filters and converts the signals received from each sub-antenna, ready for digitization. by the digitizer 24. The digitizer 24 returns the digitized information to the processor for processing. This processing comprises at least running filtering, beamforming, detection and target tracking routines on the panel data.

The processor controls the duration of activation of the currently active panel (i.e. dwell time) and, after that time has elapsed, switches to another panel and repeats the above process, storing any detected targets in memory. Cycle through the panels in sequence until all five have been activated and then proceed to repeat the cycle. Targets detected from data on one panel can be tracked as they move to a different sector, as observed by another panel. If a target of interest is found on one panel, then the processor may be willing to increase the dwell time for that panel, and may reduce the dwell time on another panel or panels where no targets have been detected.

Figure 2 shows two views of an arrangement of an enclosure 30 of an embodiment of the present invention. Figure 2a shows a perspective view, while Figure 2b shows a front view. Five panels 31ae are arranged around a quarter sphere. Each panel 31 comprises transmit and receive antennas, as described above, and has a coverage of 60° in azimuth and 45° in elevation. Three panels 31a-c are located in a lower row, while two panels 31d-e are located in an upper row. The enclosure is suitable for mounting on a wall, fence or similar vertical surface, or on a pole or mast.

A further embodiment (not shown) comprises an enclosure comprising a hemisphere, with ten panels mounted thereon, with six panels occupying a lower row and four occupying an upper row. It therefore effectively comprises two of the enclosures of Figure 2 mounted back to back. Such an embodiment is useful when 360° azimuthal coverage is required.

Other examples may have other panel configurations, or may have panels (or antennas) that have different angular coverage.

Figure 3 shows an arrangement of three radars, A, B and C, each comprising an embodiment of the present invention, which are arranged to view the respective volumes that make up a neighborhood. Each radar is networked with the others via an interface (not shown) on each radar. Thus, each radar is aware of various parameters, such as the frequency band and the direction of the active beam at a given moment, of the others. Each radar has an azimuthal scan volume that covers the other two radars. Thus, without improvement measures being taken, it will be possible for one radar to illuminate a sector containing the second radar while the second radar also illuminates a sector containing the first. In such circumstances, radiation transmitted from one radar can interfere with the desired signals received at the second radar. This is particularly problematic when the first and second radar use the same frequency band, but can also be problematic when the frequency bands used by the first and second radar differ by less than a certain frequency difference.

Therefore, each radar is arranged to select a given sector for activation based on knowledge of where the other radars are transmitting at that instant. This will wait until the radars in a given sector stop directing radiation towards it, before transmitting to the sector. Some embodiments may be arranged so that a given radar also cannot transmit to a sector containing another radar if that other radar is illuminating its own sector that is within or adjacent to the position of the given radar. This reduces the level of radiation that a given radar will receive from the transmit antenna sidebands of other radars.

For example, radar A has switchable sectors A1, A2 and A3, and radar B has switchable sectors B1, B2 and B3, where each sector corresponds to an active panel, for example as described in relation to Figure 1. The Radar A is present in sector B1 and radar B is present in sector A2. Thus, the radars are arranged so that radar A does not activate its panel corresponding to sector A2 at the same time that radar B activates its panel corresponding to sector B1. Likewise, radar C also has similarly configured sectors, which have not been shown (to simplify the figure), but would also not activate any sector that illuminates another radar when that other radar is activating its own sector that illuminates radar C.

Other embodiments of networked radars may be arranged to operate in a bistatic or multistatic arrangement, in which transmissions from one radar are received by one or more different radars. This may have benefits, including increased vulnerability to some forms of electronic attack, or may be used to provide improved radar coverage, including dwell time within a given sector or cycle time between sectors.

The radars that make up the network can be arranged, as described above, to each control their own transmissions to avoid or reduce interference. Alternatively, the radars forming a network can be configured so that there is a master radar (or other separate controller of the radars) that is aware of the layout of the radars and arranges each radar in the network appropriately to avoid any of the conflicts described above.

Figure 4 shows approximately the coverage pattern of a five-panel radar. The radar covers a span in azimuth of nominally 180° and in elevation of nominally 90°, as indicated in the ref. 40. Each panel has a transmit antenna, which has coverage indicated by the five smallest loops (drawn with a solid line) 42. Each panel has a 3 by 3 receiving sub-antenna arrangement (not shown) in a square arrangement, the outputs of each of which can be added with those of another or more subantennas to form one or more combined beams. Adding may also include changing the phase and/or amplitude of one or more of the signals from the elementary receiving antennas to manipulate the width and/or direction of the combined beam. This allows narrower beams to be produced and used for super-resolution techniques as mentioned above. The reception beam 44 is produced by the vector sum of the signals from each of the nine elementary antennas, applying an appropriate phase direction to achieve a desired direction of maximum sensitivity. Likewise, the receiving beam 46 is produced by a similar vector addition, with different phases that is oriented to direct the maximum sensitivity of the beam in a different direction. Other beams, for example, 48, 50, can be made from other similar sums and phase or amplitude adjustments being made, and used (such as with monopulse processing) to provide greater angular resolution of detected targets.

The receiving beams 44, 46, 48, 50 are all formed simultaneously using a digital beamformer and therefore act as fixed beams during activation of the particular panel.

As discussed above, the coverage beam pattern of the radar is switched, so that only a subset (typically one) of the transmit beam 42, and its corresponding antennas and receiving beams, are active at any given time, before switching. to the next subset.

Claims (12)

1. A drone detection radar comprising exactly five panels (31), each of which includes an antenna system (10), the panels being arranged on or within an enclosure that holds the panels in predetermined positions, the The enclosure comprises a quarter sphere around which the panels are arranged, in which three of the panels (31a-c) are located in a lower row of the enclosure and two of the panels (31d-e) are located in an upper row. of the enclosure, wherein each antenna system is arranged to transmit, using a transmitter (16), a signal to an associated sector, and to receive, using a receiver (20), reflected signals from targets in the sector, wherein the sectors associated with the antenna systems collectively form a monitored volume (40), and wherein a subset of the antenna systems are active at any time, wherein each subset of antenna systems is arranged to monitor their respective sector(s) for a time before a change to another subset occurs; and wherein the radar is arranged to switch to a different subset of antenna systems after each duration, so that the entire volume is monitored within a predetermined period, in which the duration for each respective sector is up to 0.2 seconds, in which each antenna system is arranged to monitor a sector of approximately 60° in azimuth and 45° in elevation. 2. A radar as claimed in claim 1, wherein the predetermined period is a period of every second, or every half second. 3. A radar as claimed in any of the preceding claims, wherein each subset of antenna systems comprises a single antenna system. 4. A radar as claimed in any of the preceding claims, wherein the radar is arranged to monitor a nominal volume of 180° in azimuth and 90° in elevation. 5. A radar as claimed in any of the preceding claims, wherein each antenna system is connected to a common processor (12) which is arranged to process digitized signals from each antenna and to provide an alert if the signals are characteristic from being reflected from a drone. 6. A radar as claimed in any of the preceding claims, wherein the radar is arranged to vary the dwell time spent in a given sector according to whether the target has been detected within that sector. 7. A radar as claimed in any of the preceding claims, wherein the antenna system (10) of each panel comprises a transmitting antenna and a receiving antenna. 8. A radar as claimed in claim 7, wherein each receiving antenna comprises a plurality of elementary receiving antennas, each of which has a beam pattern that is configured to be combinable, in the radar, with beam patterns. beam from one or more respective elementary receiving antennas, to produce one or more narrower beams in a given direction. 9. A radar as claimed in claim 8, wherein the radar is adapted to manipulate the phase and/or amplitude of the elementary receiving beams during combination with other beams, to adapt the beam direction of one or more beams. narrower. 10. A plurality of radars, each according to any preceding claim, wherein each of the plurality of radars is arranged within a neighborhood, and is synchronized such that two radars cannot transmit radiation within the neighborhood. same frequency band in a sector visible to two or more radars within the neighborhood at a given time. 11. A plurality of radars, each according to any of claims 1 to 9, wherein each of the plurality of radars is arranged within a neighborhood, and is synchronized using an interface, so that no Two radars are allowed to transmit to each other simultaneously on the same frequency band. 12. A plurality of radars, each according to any of claims 1 to 9, wherein each of the radars is arranged in a neighborhood, and are synchronized such that a first radar is configured to receive and process target returns from signals transmitted by a second radar.